format PE64 GUI
entry start

include 'win64ax.inc'

section '.text' code readable executable

        start:
                sub     rsp,8*5
                mov     r9d,0
                lea     r8,[_caption]
                lea     rdx,[_text]
                mov     rcx,0
                call    [MessageBoxA]
                add     rsp,8*5

                nop
                nop
                nop
                nop

                sub     rsp,8*5
                invoke  MessageBoxA,0,_text,_caption,0,MB_OK
                invoke  ExitProcess,0

section '.data' data readable writeable

        _caption        db  'Test',0
        _text           db  'Hello World',0

section '.idata' import data readable writeable

        library kernel32,'KERNEL32.DLL',\
                user32,'USER32.DLL'

        import kernel32,\
               ExitProcess,'ExitProcess'

        import user32,\
               MessageBoxA,'MessageBoxA'
    

Code:

                invoke  MessageBoxA,0,_text,_caption,0,MB_OK