I usually buy long-fit short sleeved t-shirts, black and plain ("aniconic"), in European medium size at different H&M branches in Bangkok; I don't recall finding such shirts in any other shop in malls or in any market.
As I recall, it always cost me 400 ("399") Baht in H&M and this always felt to me like a rip off because I bet the shirt (production, transportation and sorting) doesn't cost H&M more than 50 Baht to perhaps be exaggerating, and because if I buy groceries at Klong Toey market (which is Bangkok's largest wholesaling food bazzar), I could pay the same price for about 7.5 kilos of food which could last for at about 3 weeks.
Where can one buy long-fit short sleeved t-shirts in Bangkok, preferably in European sizes, in less than or equal to 200 Baht?