if your ticket in 1 pnr , u should get all your boarding pass at cgk , if your ticket in different pnr , if cgk agent wiling to help to insert booking in system , u also can get all your boarding pass due both airline using same system. if you never get you sin-bkk boarding also never mind, jus proceed to transfer c or d in T1 wher tg operating terminal (transfer c better, sometime transfer d no staff due lack manpower). yup, sin all 3 terminals are connected both after or before immigration. lookout signage, very easy to find