try this:
local x,y = guiGetScreenSize()
addEventHandler("onClientRender", root, function()--nothing is returned
local level = exports.exp_system:getPlayerLevel ( localPlayer)--thePlayer isn't defined, use localplayer
local Name, Expreq = exports.exp_system:getLevelData ( level )
dxDrawRectangle ( x/4.59, y/100, x/2.2, y/12, tocolor ( 0, 0, 150, 150 ) )
dxDrawText ( "Exp: "..Name..", "..Expreq, x/4.59, y/95, x, y, tocolor ( 0, 222, 10, 255 ), 1, "bankgothic" ) --Added name and Expreg
end)