Relations between Cambodia and Thailand remain problematic. The Thai government continues to suspect Hun Sen of supporting a self-exiled former Thai prime minister, Thaksin Shinawatra, and the dispute over the territory surrounding the ancient Preah Vihear temple on the Cambodian-Thai border has yet to be resolved. The stand-off escalated in early February into the most serious fighting yet as Cambodia and Thailand exchanged heavy artillery fire, killing at least 11 people. Attempts to resolve the dispute by Indonesia, which presently holds the rotating chairmanship of the Association of South-East Asian Nations (ASEAN), have accomplished little. In early April the Thai foreign minister, Kasit Piromya, boycotted two days of Indonesian-brokered talks, suggesting that any progress will be slow. Cambodia and Thailand also have yet to resolve the disputed sovereignty of resource-rich maritime areas in the Gulf of Thailand.

Rivalry between China and the US for influence in Cambodia is set to intensify in 2011-12. China has become an important partner for Hun Sen's government, owing in part to its cancellation of Cambodia's debt repayments falling due in 2010, as well as its financing of large-scale infrastructure projects. Unlike US assistance, which is typically conditional on greater respect for human rights, China's assistance has come without such strings attached. Cambodia's relations with Vietnam will be close while Hun Sen remains in power.