Having flown long haul east & west, I've changed my timings once over there, despite over lapse or delayed. If splitting it, stick to morning time & evening when there (GMT), as body clock won't change strange away either, so take your evening/night insulin, then the next day change to the time you're in. Obviously check BGs regularly to correct highs, depending on activities you choose to do whilst there!! Which part of Thailand are you staying in? Enjoy anyway!!