Why specifically are you wanting to do this? I highly suggest not tampering with the basket. Those values need to updated properly through API. Just changing the value directly in database for example will not tell CBSubs that the basket has been processed.
If you want the basket status to output as a field I suggest using a CB Query Field with the below query.
Code:
SELECT `payment_status` FROM `#__cbsubs_payment_baskets` WHERE `user_id` = '[user_id]' ORDER BY `time_initiated` DESC LIMIT 1
The above will give the payment status of the most recent basket for a user and output it as a field using CB Query Field.