I've lived alone in Bangkok for nearly 20 years now.
I did live briefly in Khao Lak, 5-months, as I came to Thailand, on work, just after the Tsunami, but moved to Bangkok in January 2006. It's a wonderful city to live in, the arts, cinema, wonderful parks, I bicycle everyday, nearly everywhere.
I could walk anywhere in Bangkok and feel safe anytime of the day or night, that's critical.
My Thai is adequate, but minimal. BTS/MRT/AirportLink go everywhere now.
In all these years, I've never felt homesick, no once. The two times that I did briefly return for a week in 2006 when my father died, and later a for a week to renew my then B-visa. The first time was unavoidable, the second, complete waste of time. If I never see that country again I wouldn't miss it.
I see absolutely no issues about living alone, if that is your preference and you're secure in yourself.
It's really more of a personal issue, no mater where in the world you choose to live.