He reportedly said the decision followed his failure to bring down lottery price as ordered by the government.
Somchai has submitted his resignation to Permanent Secretary of Finance Rangsan Siworasat and has informed Deputy Prime Minister MR Pridiyathorn Devakula, Finance Minister Sommai Phasee and Deputy Finance Minister Wisudhi Srisuphan of his decision.
The government has promised to bring down lottery prices to Bt80. Several governments have failed in this mission. A special fee is normally charged as a result of the multi-layered marketing system.
Rangsan said he would discuss the appointment of Somchai's replacement with the finance ministerce.
Somchai’s resignation will be effective on April 27.
Prime Minister Gen Prayut Chan-o-cha said on Sunday that he would exercise Article 44 under the interim charter to appoint the new chairman.
"This would appoint someone entrusted to handle the task. If the replacement can't accomplish it, he will be replaced," he said.