Bates, 29, will feature for the county in the 50-over competition alongside former England captain Charlotte Edwards, who joined them in December.
The right-hander will also rejoin Southern Vipers in the Women's Super League after the World Cup.
She scored 232 runs at an average of 42 as the Vipers won the inaugural Super League title last season.
New Zealand women's captain Suzie Bates will play for Hampshire women ahead of the Women's World Cup in June.