Thailand is Indochina time (ICT +7 GMT). During the European summer, ICT is +6 hours from BST and in the European winter, ICT is +7 hours when compared to GMT.
In summer, (June 21) sun-rise on mid-summer's day is at 5.50am and sunset is at 6.50pm with 20 minutes of twilight either side.
In winter (December 21), sun-rise is at 6.40am and sets at 6.00pm with similar twilight as the summer.
The longest summer day has 12 hours 56 minutes of daylight and the shortest winter day has 11 hours 20 minutes.