BEIJING, Jan 5 (Reuters) - China’s foreign ministry said on Monday that a ceasefire agreement between Thailand and Cambodia was being gradually implemented and expressed hope that both sides could ensure a "comprehensive and lasting" end to hostilities.

The two Southeast Asian neighbors agreed to a second ceasefire in late December to end several days of border skirmishes that broke out after the Thai military launched a renewed offensive, which Cambodia characterized as a violation of an earlier truce.

"China hopes that both sides will ensure a ceasefire that is comprehensive and long-lasting," Chinese foreign ministry spokesperson Lin Jian told a regular press briefing in Beijing.

Lin also noted that the Thai side had returned 18 soldiers to Cambodia, a move seen by regional observers as a key confidence-building measure following the recent spike in tensions.

The border dispute, which centers on contested territory near ancient temple sites, has periodically flared into violence over the last decade. The latest round of fighting has caused thousands of civilians on both sides of the border to flee their homes.

China, which maintains close economic and diplomatic ties with both Bangkok and Phnom Penh, has been urging restraint, fearing that prolonged instability could affect regional trade and security.