Transit to gua

Hello, I am a Banngladeshi national. I will be flying with China southern airlines for my connecting flight (return ticket) with a transit time of 1 hour 30 minutes for my first flight from Seoul- Guangzhou-Doha and 4 hour layover on my return flight from Doha-Guangzhou-Seoul. While booking the tickets from third party app, I noticed there maybe a visa/transit visa requirement which makes me question. Since the airport I will be transitting in is Guangzhou Baiyun International Airport, I was wondering if I am eligible for the 24 hour visa free permit or do I require a Chinese transit visa for my connecting flights eventhough my layovers are less than 5 hours on each flight?