Thanks for the replies guys.
Transiting through ARN or CPH is more that OK with me, as I have to transit through AMS or CDG (probably the most dreadful airport in the world) today.
SK has good connections from TRD (where I live) to ARN or CPH through OSL. Btw, CPH and OSL are both very nice airports. Have never been to BKK, but AF flies through SIN which I think is very nice.
Anyway, my impression from what you say is that I can't go wrong with either SQ or TG. I think I'll have to base my decision on price and connection times. Since they are both *A, I'll probably check out both of them.
Btw, SQ is using 777s on both PER-SIN and SIN-CPH, whereas TG use 744 on both PER-BKK and BKK-ARL, right?