My parents planning to get a family MPV that can seat at least 6 people. New or used it don't really matter as long as its comfortable for long distance. They have a budget of max RM100k.

They are looking at
- Brand New 2020 Honda BRV
- Brand New Perodua Aruz

I'm suggesting
- 2011 / 2012 Toyota Vellfire 2.4
- 2011 / 2012 Toyota Alphard 2.4
- 2018 Toyota Innova 2.0G

We travel alot and have plans to drive all the way to Thailand / Singapore. What is the best choice and hows the maintenance like on those cars ( if you've owned one, do let me know the running cost )

If it's brand new - Proton Exora RC will fit the bill.
Proper MPV. Not a 5+2 Mpv

Nay Sayers / Anti Proton will bash but this is probably the most affordable MPV after (new) Innova. The new Exora facelift has some improvements already.

Driving one now (Not the RC version). Have driven up North, down Singapore and to the east of Kuantan. Reliable.
Gearbox and Turbocharger still working.
No breakdown after 5-6 yrs of owning except for a sudden dead battery.

Can't think of any proper full size 7 seater which is around this price range. The former Sienta is like a baby Alphard. Probably the size of Aruz.