Fortigate as PPOE dialer. Setting modem/router as a bridge mode from your Telekom Malaysia router / modem , Maxis , Redtone is easy. Follow this step. BUT…Before you start, make sure you have your account username and password from your obtained from your ISP.
UNIFI : data vlan ID : 500
REDTONE : data vlan ID : 620
MAXIS : data vlan ID : 621

Login to you fortigate and create new interface as follow.
Create new UNIFI interface via CLI > Mode : PPPOE role as WAN and bind to WAN interface. :

config system interface
edit UNIFI
set vdom root
set mode pppoe
set distance 1
set allowaccess ping fgfm
set role wan
set username realitymaya@unifibiz
set password realityfantasy2020
set interface wan
set vlanid 500
next
end

For streamyx account. Follow this.
Create new interface type : PPPOE > role as WAN > bind to wan port interface.
config via CLI :-

config system interface

edit "STREAMYX"
    set vdom "root"
    set mode pppoe
    set type tunnel
    set role wan
    set interface "wan"
next

end

Follow this in GUI > APPLY

For Policy : lan > STREAMYX / UNIFI > nat enable

config firewall policy
edit 1
set name “LAN_INTERNET”
set srcintf “lan”
set dstintf “STREAMYX” “UNIFI”
set srcaddr “all”
set dstaddr “all”
set action accept
set schedule “always”
set service “ALL”
set utm-status enable
set webfilter-profile “default”
set application-list “default”
set ssl-ssh-profile “certificate-inspection”
set nat enable
next
end

and lastly for routing.

config router static
edit 1
set distance 5
set device “UNIFI”
set dynamic-gateway enable
next
edit 2
set distance 20
set device “STREAMYX”
set dynamic-gateway enable
next
end

Thank You.