\documentclass{article}
\usepackage{hyperref}
\usepackage{showframe}
\begin{document}
\begin{Form}
\noindent\TextField[name=a,width=2cm,charsize=8pt, height=.5cm]{}
sometext \TextField[name=a,width=2cm,charsize=8pt, height=.5cm]{}
\vspace{4ex}
\def\LayoutTextField#1#2{% label, field
\def\temp{#1}%
\ifx\temp\empty
#2%
\else
#1 #2
\fi
}
\noindent\TextField[name=a,width=2cm,charsize=8pt, height=.5cm]{}
sometext \TextField[name=a,width=2cm,charsize=8pt, height=.5cm]{}
\vspace{4ex}
\end{Form}