BANGKOK—Thailand will no longer seek China’s financial backing for a high-speed rail line connecting Bangkok to the provincial hub of Nakhon Ratchasima, opting to finance the project on its own, its transport minister said Friday.

Thailand has been struggling to secure what it considers a satisfactory financing deal from Beijing for the 250 kilometer (155 mile) rail line, seen as part of a broader network running from southern China through Laos, and south through Thailand and Malaysia to Singapore.

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