Combining Backups

Hi, I lost my phone when I was staying overseas and created a new whatsapp account with my overseas line. I'm back in my home country now and would like to switch back to my old whatsapp number. Is there a way I can keep both numbers' conversations?

– overseas line: Cambodia number
– old line: Singapore number

– will the conversations in my Cambodian number be combined with the conversations backed up with my Singapore number if i switch it? Or will the switch overwrite my Singapore number back-up and I'll lose my old conversations?

I hope you get the question I'm trying to ask! Hope to hear from you soon. Thank you.