I’ve done all the *G lounges at BKK (origin pax so didn’t need a shower). The best for me by far are the SQ and BR lounges (SQ better but BR has the wacky neon lights so worth a visit). The TK lounge was pretty meh (nowhere near as good as their IAD lounge) and the less said about TG the better.

Personally I’d much prefer to connect at SIN. You get straight onto the concourse with security at the departure gate. And there’s so much to see that could kill a couple of hours or more before you even consider a lounge. The only lounges I used at SIN were SQ’s business class lounges in T3 (excellent) and T2 (disappointing). I’d assume their *G lounge is a notch down from those. Having heard about the poor SQ *G lounges there if flying Y I’d switch to Priority Pass.