We're doing it in April to get to Bali. I've done cnx thru NRT several times (ICN is another backup w/KE cnx if needed)
Where are you going in Thailand? I just went this past spring--just Bangkok and Hua Hin and Ampawa.

We're flying MSP or ATL (777 flat beds) or 744 DTW (almost flat) thru NRT to BKK.
Then ezeds on Thai (must be bought online thru travelnet, myidtravel) to Bali.
Another option would be DTW/HKG nonstop w/connections to DPS via Cathay or Garuda nonstops.
SIN is also option, but not our first choice since it's unfamiliar to me.

I have 4 buddies going to Thailand in March. They'll be flying to NRT from 2 gateways and meeting on DL flt to BKK. If I can help any way, please ask. We have sev folks here who do the tricky travel (see Siem Reap by Taxi report!)
I have pal who dates FA for TG and he always talks about how full the flights are and how hard it is to NR. he jumpseats often.