SIN has convenient smoking rooms inside the terminals
TPE has smoking rooms inside the terminal - small and crowded. Could use better exhaust fans.
DEL, BOM, HYD, COK, TRV (most airports in India) all have smoking rooms inside the terminals
AUH, DOH have smoking rooms inside the terminal
Inconvenient:
CDG has one tiny smoking booth for incoming passengers in Terminal F. All other terminals - you have to exit the building, and re-enter through immigration and customs. Visa needed to exit the building.
LHR - total ban inside the terminal. Visa needed to exit the building.
LHR T4 has a smoking area in the departure area. Clearly signposted.