Spoken Thai is everywhere in Bangkok as soon as you leave lower Sukhumvit, CBD, Khaosarn.
I went to Bang Phli today for some shopping. I went by public transport, asking for directions many times, and I had to call the shop in advance to ask about address, opening hours, stock.
I didn't speak anything else than Thai, and didn't hear anything but Thai (ok, the old lady who sold me 3 bananas said "twentyfive baht", but when I asked her for the bus stop, she switched to Thai). I saw 2 foreigners.
Written, that's different. In Chinese, I had to fill out banking forms in Chinese, including the long forms of Chinese numerals. The instructions for my answering machine were in Chinese. My computer used Chinese Windows. Here, too much of the written things in daily life are in English.