This is one of the most useful traffic signs for city driving. If you cannot read it and you stop at the red light then cars behind you will be honking their horn. It says in Thai “lieow sai paan dta-lot” which basically means turning left you can pass at all times. So, no need to stop for the light. Be careful though, there is another sign that says “turning left wait for the green light”!
เลี้ยว ซ้าย ผ่าน ตลอด (lieow sai paan dta-lot)