First selecting a motorcycle is a very personal thing, and without knowing what you look for in a motorcycle it's difficult to give any advice.
Both the Tiger Boxer 250 RS and the Lifan LF250-B (Custom V250) are at the same price level (70 to 80,000 THB). The Tiger Boxer 250 RS is what we would call a sporty 250cc all-round machine, while the Lifan Custom V250 is a 250cc v-twin cruiser.
Both motorcycles are made in Thailand, and are of good quality (considering the price). Tiger Motor announced a Tiger Boxer 250 RS with fuel-injection, but currently we have no idea what the fuel-injection model will cost or what the benefits are on fuel economics.
Basically the choice between the two motorcycles will be on your personal preferences and the riding position you like... The only good advice, I can give, is that you contact both Tiger and Lifan for a test ride