.S. Military Units Quietly Shut Last 2 Major Bases in Thailand New York Times - June 20, 1967      BANGKOK, Thailand, June 20 (AP)--The United States military quietly closed its last two major installations in Thailand Today      A spokesman said that there had been "no turnover ceremony as such" as Americans left U Taphao Air Base on the Gulf of Thailand, which served as a staging center for United States B-52 bombing runs into Cambodia and Vietnam at the height of the Indochina war.      The military also shut down the Ramasun electronic monitoring facility in northeast Thailand, the spokesman said.      Under an agreement with the Thai Government March 20, all United States military personnel must be withdrawn from from this country by July 20 except for 270 military advisers. Students Backed Accord      Thai student groups have demonstrated for strict enforcement of the pact by the Government of Prime Minister Seni Pramoj, which took office after the agreement was reached and is more friendly to the United States than the previous one.      The number of United States military personnel in Thailand was down to about 700 today, from a peak of 50,000 during the Indochina war.  Americans were stationed at seven air bases and numerous other installations, with as many as 9,000 at U Taphao.      U Taphao's 11,500-foot runway was opened in 1966, putting B52's just 45 air minutes from targets in Indochina.  The nearest alternate heavy bomber base was on Guam, six hours from the war area.      The Ramasun station was a center for monitoring radio communications of Communist forces in China and Southeast Asia.  After the Indochina war ended last year, Ramasun's operations mainly supplied Thailand with intelligence information. Access to Facility Restricted      But the Americans kept Ramasun off-limits to all but a few authorized Thais.  The Thai Government said that anything less than full access violated Thai sovereignty.  The new Government reviewed the matter, but the two sides were unable to reach a compromise.      The Thai Foreign Minister, Bhichai Rattakul, said yesterday that the United States would give Thailand monitoring equipment that was "of use to Thailand."  The Thai military, reportedly unhappy with the civilian Government's decision to make the American forces leave, had lobbied for retention of some equipment to be used by Thai technicians.