OK, that's a bit more info, so not exactly a 'beach' holiday. Phuket Town is great, especially since the buses are running again.
First 10ish times overnighting in BKK, I hated it, but didn't explore. When I did, now, considerate one of the best places to visit in Thailand, if not going for Andaman Sea 'beach' holiday. Or Surat Thani / Phang Nga area.
Has all the good & bad, of a huge metro, with lots of gems, out of the slum tourist areas. Plenty of hostels to choose from, or inexpensive private rooms. Overall cost about the same, along with great bus system, aside from rush hour. Whole area is in gridlock anyway, BTS/MRT might be faster, if making the 1st trains, though I really do prefer the buses. Planning essential of course.
Canal market, riverside is usually where we hang out during the day. Actually prefer the west side of the river; Khlong San & Bangkok Noi (Wang Lang) areas.
Bang Rak or ChinaTown / Rattanakosin Island works well also.