Thailand's mineral reserves had not been well assessed in the 1980s. Mining and quarrying accounted for only a small share of GDP, in 1986 amounting to about 2 percent of the total in real terms. About thirty minerals were exploited commercially, but many were of minor significance. Tin, tungsten, fluorite, and precious stones were important foreign exchange earners in the early 1980s and so, to a lesser extent, was antimony. Minerals of substantial value to the domestic economy included lignite, gypsum, salt (which was also exported), iron ore, lead, manganese, limestone, and marble.

Tin was the leading mineral. The existence of tin in the area of present-day Thailand was known at least by the thirteenth century, when it was alloyed with copper in casting bronze images of the Buddha. In the 1980s, major workings were located in the southern peninsula, although deposits were also found and worked in several other parts of the country. The ore was obtained from onshore alluvial deposits, weathered and disintegrated formations, river beds, and offshore deposits along the seacoasts.

Production of tin concentrates averaged over 29,000 tons annually in the early 1970s, dropped to about 22,000 tons in the mid-1970s, and then rose to 46,000 tons in 1980. By 1985 tin production had dropped to about 23,000 tons as a result of export controls imposed by the International Tin Council and the indefinite closing of a major offshore mining company. The actual output of concentrates in the 1980s was believed to have been at least 10 percent higher than officially reported. The additional quantity represented tin concentrates smuggled from the country to escape payment of both business taxes and the statutory royalty deducted from the price paid to the seller by the foreign-controlled Thailand Smelting and Refining Company (THAISARCO). The export of tin ore and concentrates was banned by the government after THAISARCO began smelting tin in 1965 at a newly constructed plant on Phuket Island. Most of the smuggled concentrates originally went to Penang, but this trade had been largely halted by the Malaysian authorities in the 1980s, the illegal ore was sent to Singapore for smelting.

Since the mid-1970s, the tin-mining industry has generated a large amount of political controversy, social unrest, and illegal activity that continued into the mid-1980s. Onshore mining operations were carried on mostly by small miners who were predominantly Thai. Offshore operations included a number of large dredges owned by both Thai enterprises and foreign firms, as well as thousands of suction boats. Both kinds of operations were supposed to be registered with local provincial authorities. The tin fields had attracted large numbers of the unemployed or persons seeking fortunes, however, who mined illegally. Reports of a new tin strike brought thousands of individuals to the area, resulting in such attendant social problems as claim jumping, forged registration certificates, frequent violence, and the like. In 1975 the government-owned Offshore Mining Organization (OMO) was set up to replace large offshore oil c 1000 concessions owned by foreign corporations and ousted Thai government leaders. A substantial amount of illegal dredging was also reported in the OMO concession area, whose size and restrictions of exploitation to subconcessionaires had created strong resentment among independent small operators, even though the OMO had given concession rights to a considerable number of them. In late 1979, a group of nonconcession-holding small dredgers pressed the provincial authorities of the area to urge the central government to revoke all restrictions on mining in the OMO holdings. The overall magnitude of illegal operations appeared in the early 1980s to be beyond the ability of the local authorities to control. Official action, moreover, was often deterred by public sympathy for the poor person struggling to eke out a living.

Thus, illegal mining was an important source of employment in the southern peninsula and, in conjunction with related illegal operations, created numerous ancillary jobs. From the national viewpoint, however, a great loss of natural wealth occurred because of haphazard and inefficient exploitation. Onshore miners, legal and illegal, tended to take out only the readily accessible richer ore, leaving varying amounts of lower grade ore that, mined separately, was uneconomic. Large numbers of small dredges sent divers down to find rich spots that were sucked up, avoiding large nearby areas containing ore that was costly to mine. Many of the dredges also had poor separation equipment, and considerable quantities of ore were lost in the tailings. Because of potential political problems, decisive action by the central government (or provincial governments) to resolve this problem did not appear imminent in the late 1980s.

Thailand is a rich source of sapphire, ruby, zircon, garnet, beryl, quartz, and jadeite, and in 1986 gems and jewelry were a large export item in terms of value. Significant deposits of rubies were located in Chanthaburi and Trat provinces in the southern part of the Center, and deposits of sapphire were found in Kanchanaburi Province. Stones were also imported from Sri Lanka, Australia, Africa, and South America for cutting and setting into jewelry. By the mid-1980s, Thailand had become one of the world's major gemcutting centers, and the craftsmanship of Thai gemcutters was widely recognized.

Tungsten, an important source of foreign exchange earnings beginning in the early 1970s, was found in the mountains in the North and in the Bilauktaung Range along the Burmese border. In 1970 a major find of the tungsten mineral wolframite was made in Nakhon Si Thammarat Province in the South. Antimony, also an important export, was found in many parts of the country. Mining was carried on almost entirely by small operators, but in the mid-1970s cumulative annual production was about 6 percent of total world output. Fluorite, one of Thailand's principal exports, was mined mainly in the North in Chiang Mai and Lamphun provinces, where large reserves existed. Relatively large deposits of rock salt of approximately 97 percent purity underlay areas in the Northeast. Reserves were estimated to be at least 2 billion tons. Although having great future export potential, the lack of an adequate transportation infrastructure posed a major problem for exploitation of the rock salt reserves.

Offering a hopeful promise of a new source of foreign exchange earnings and savings on imports in the 1980s was the long-delayed development of zinc mining and refining. This involved exploitation of a large ore deposit, estimated at 3.5 million tons of 25 percent content, at Mae Sot in Tak Province near the Burmese border. A zinc smelter constructed by a ThaiBelgian consortium began operation in 1984.

Data as of September 1987