The first few times I went to Thailand, I used EVA.
One time, I paid £420 (economy) return, which at the time was cheap.
But I got tired of the flight times. Leaving LHR in the evening was alright as it gives most of the day to get there with no rush. I used to fly out in November or December, so once again the evening take off was good as I could get to LHR in daylight.
What I came to dislike and hence why I stopped using was the landing time and Thai Airways.
The flight is supposed to land about 4pm (from memory, could be slightly out on this)
Anyway, the flights I was on always landed late, and the baggage always seemed to take a long time.
Meaning getting to the hotel gone 7pm. When friends do the same flight no delays WTF!?!?!?
On one trip I wanted to go to Udon Thani first, so I looked around. Rather than EVA then have to book another flight I found Thai did a multi-city ticket, so I booked. Cost more than EVA but less hassle. LHR to BKK then onto Udon.
Take off at 12.30 pm on the A380 was nice, and by 1pm the next day I was walking down to road from my hotel in Udon.
Since then, I like the 12.30 pm take off from LHR. Gets me into BKK early, which I like.