A TRAVEL expert has warned that Hong Kong people travelling in Southeast Asia have become a popular target for thieves and robbers. Sam Wong, Manager of Thomas Cook Travellers Cheques Ltd, said the increase in crimes against travellers from the territory was indicated by the number of refunds the company made on travellers' cheques. Thomas Cook has recently appointed refund agents in Ho Chi Minh City, Hanoi and Phnom Penh. The biggest rise in crime against travellers was theft from passengers taking non-government overnight buses, he added. ''In some cases the victims are choloroformed before having all their valuables stolen,'' Mr Wong said. Another crime involved local criminals pretending to be friendly. They invited tourists to their home for refreshments which turned out to be drugged. When the victims were incapacitated, they were robbed. Other frequent types of crime against travellers were theft from hotel rooms and pickpocketing. ''You can't avoid being robbed, but you can take precautions to avoid losing everything,'' Mr Wong said. Mr Wong reminded tourists not to take out more money than they needed for the day and to keep everything else locked up in a hotel safe deposit box.