Just made a BTC payment to a merchant which uses BitPay for processing and total amount was just lower than $3k. Have not been asked KYC.

I'm wondering if I use the same merchant again, will the next transaction add towards the $3k limit or can I keep doing multiple transactions without KYC?

The one-time verification requirement is for people making BitPay merchant or prepaid payments of $3,000+, initiating refund requests for amounts of $1000+, or receiving BitPay payouts. Business users making purchases, etc. within these thresholds will also complete ID verification as individuals. Person-to-person payments with BitPay's BitPay and Copay apps aren't included and do not require ID verification.