“By the time Air Force Captain Bill Oyler made it to Nha Trang Air Base above Cam Rahn Bay to fly with the Ninetieth Operations Squadron, gay airmen in the States had filled his address book with the names of scores of other gay pilots stationed there. Between Nha Trang and the larger Tan Son Nhut base near Saigon, Oyler knew about one hundred gay pilots. When he transferred to Thailand, he met between 150 and 200 more gay Air Force personnel.”
Conduct Unbecoming: Gays & Lesbians in the U.S. Military by Randy Shilts, page 149.
Capt. Bill Oyler arrived in Vietnam in 1971.
See this quote for what life was like in the rear areas of Vietnam during the early years of the war.