One of several deals to SE Asia from Seoul. ICN legs are either 787 or A350; SIN legs are usually A321regional business class, though they used to fly the A350 on this route at least sometimes so maybe you'll get lucky.

Plenty of dates between October and next July, including Saturday departures. Prices range $690 - $730, depending on dates. Bookable direct. Random searches seem to always show at least 1 long layover (9+ hrs), but, again, maybe you'll get lucky on your day.

Sample date.

Never flown VN, so no firsthand experience. Service reviews seem to say crews are "hit and miss" but usually very friendly. Looks like they've upgraded the 787s and A350s to reverse herringbones.

This airline might not be tip top, so it might not be a nice enough experience to count as a "deal" to some much more demanding flyers.