We can arrange the custom fields in suitelet by following methods
field.updateLayoutType({
layoutType : serverWidget.FieldLayoutType.NORMAL});
var htmlHeader = form.addField({
id: 'custpage_header',
type: serverWidget.FieldType.INLINEHTML,
label: ' '}).updateLayoutType({
layoutType: serverWidget.FieldLayoutType.OUTSIDEABOVE}).updateBreakType({
breakType: serverWidget.FieldBreakType.STARTROW})
we can adjust row wise and column wise
OUTSIDEABOVE
OUTSIDEBELOW
STARTROW
MIDROW
ENDROW
STARCOL