He was elected MP for Hindon again in 1625 and was re-elected MP for Hindon in 1626 and 1628. Among the estates Thynne inherited was one at Kempsford in Gloucestershire, where he built a new country house, demolishing an important fortified manor house which since the 13th century had defended a crossing of the River Thames. Thynne died on 1 August 1639.