The Office of the Prime Minister (Abrv: OPM; Thai: สำนักนายกรัฐมนตรี, RTGS: Samnak Nayok Ratthamontri) is the central executive agency in the Government of the Kingdom of Thailand.

It assists prime ministers in the execution of their duties and helps them manage and formulate policies.

The prime minister must appoint a permanent secretary in charge, who is also a member of the cabinet, to oversee its operations.

In late 2016, the OPM acquired an additional function: as a "holding pen" for government officials accused of corruption.

Former Prime Minister Prayut Chan-o-cha invoked his special powers under Section 44 of the interim charter to create 50 posts at the OPM for civil servants being investigated for alleged wrongdoing.