We flew from Singapore to Tokyo using Thai Airways, with 1 stop at Bangkok. This is the cheapest non-budget flight available which we can find at a short notice (There's also China and Philippines airlines which are slightly cheaper but the transit duration is too long).
The Thai airway staff are courteous, friendly and always smile at you. Their service on board is good as well.
Not bad at all.
From Singapore to Tokyo, we took Boeing 777/747.
From Tokyo to Singapore, we took Boeing 747/A350
A350 is very new, and with spacious leg-room.