BANGKOK, June 25 (Reuters) - Thailand will sell 50 billion baht ($1.57 billion) of government savings bonds next month to finance relief measures, the finance ministry said on Friday, as the Southeast Asia nation battles its biggest coronavirus outbreak so far.

The proceeds will be for spending measures, including a co-payment scheme and cash handouts for low-income people, Patricia Mongkhonvanit, head of the ministry's public debt management office, told a briefing.

Last month, the cabinet approved an additional economic relief package worth 255 billion baht ($8 billion) to help people affected by the latest outbreak.

The bonds, to be offered from July 5 to 23, are three-year issues with an annual average coupon of 1.8% and four-year issues with a 1.9% coupon on average, the ministry said.

The debt is part of a 1 trillion baht borrowing plan announced last year in response to the pandemic. ($1 = 31.77 baht) (Reporting by Kitiphong Thaichareon Writing by Satawasin Staporncharnchai; Editing by Martin Petty)