Modify \masm32\examples\exampl01\generic\generic.asm:
.elseif uMsg == WM_PAINT
invoke DefWindowProc, hWin, uMsg, wParam, lParam
invoke GetWindowDC, hWin
push eax
.data
include \masm32\include\gdi32.inc
includelib \masm32\lib\gdi32.lib
txHello db "Hello"
.code
invoke TextOut, eax, 200, 5, offset txHello, 5 ; needs gdi32
pop eax
invoke ReleaseDC, hWin, eax
This works for non-Aero Windows only.