The highly-regarded Bates was released by Hampshire at the end of last season and is currently out of contract.
He made his debut for Somerset Seconds on 18 May in two back-to-back T20 games against Sussex at Horsham and then played a three-day Second XI Championship game starting the following day at Woodman Cote.
The 24-year-old was back in action at Taunton Vale this week, appearing in two T20 games for the Seconds against Glamorgan on Tuesday and then taking part in a three-day championship match against the same opposition.
Bates was tipped by some as a possible replacement for Craig Kieswetter after it emerged that the Somerset keeper’s eye injury would keep him out for most, if not all, of the 2015 season. Somerset however backed their two existing young keepers Regan and Alex Barrow, who has played in all the first team matches so far.
Bates is respected as one of the best glovemen on the circuit – his average catches of 3.5 catches per match in 2010 is a Hampshire record for a season. However his batting has failed to match his excellence with the gloves and after 46 first-class matches he averages just 21.20 with one century and five half-centuries. He has yet to record a half-century in either List A or T20 cricket.
He is though an experienced player and Somerset will have taken the opportunity to have a close look at what he can offer during the past two weeks.
Bates has so far taken nine catches and made one stumping in all games for Somerset Seconds over the past two weeks and made one half-century, an attacking, unbeaten 53, batting at number four in one of the T20 games with Glamorgan. He faced just 34 balls and struck four sixes as Somerset chased down their target with more than an over to spare to win by five wickets. He also scored 33 at number four in the Second XI Championship game with Glamorgan.
Earlier this season he turned out Essex Second XI in three games as well as in a match for minor county Wiltshire against Devon.