(Photo: Latbin Bonnak, circa 1950, the National Archives)

Above: The Phra Ya Sombat Phaisan Building

Fact file: Bangkok's tallest buildings over the years

Rama IV era - Wat Arun - 70 m (not strictly a building, but a tall structure)

1925-1926 - Nai Loed Building near Saphan Phitthayasathian (Saphan lek Lang)-- HQ of Nai Loed Co. Ltd. (Nai Loed Setthabut--Phraya Phakdee Noraset (1872 - 1945) was the pioneer of the Bangkok bus and boat system as well as the agency for selling Esso Oil--then Socony Oil)

1927 - Phra Ya Sombat Phaisan Building - 7 stories

1966 - AIA (American International Assurance) building on Surawongse Rd - 10 stories

1970 - Cathay Trust Building (Esso Building) on Rama IV Rd, Silom - 12 stories
1970 - Dusit Thani - 82 m
1970 - Chokechai Building - 22 stories

1978 - Royal Orchid Sheraton - 101 m

1982 - Bangkok Bank (Silom) - 134 m

1987 - Baiyoke I - 151 m

1996 - ThaiWah 2 - 196 m

1996 - Jewelry Trade Center - 221 m

1997 - Baiyoke II - 304 m

For comparison, the current world's tallest building is 509 meters tall.

Thanks to Nils, Pas, The Enforcer!, Wisarut and others on the forum who contributed.